Apparatus for cleaning a residual image from a photosensitive member

ABSTRACT

A residual toner image remaining after transfer of a developed image from a photoconductive surface is cleaned therefrom in one embodiment by a conductive cleaning brush mounted in a vacuum chamber and having a flicker bar which is used to apply a potential to the brush opposite that of the residual toner particles to be removed from the photoconductive surface. In another embodiment, the brush is divided into a number of electrically insulated segments so that the polarity of the potential applied to a portion of the brush coming in contact with the photosensitive surface is opposite to the charge on the residual toner particles and a potential applied to a segment spaced from the photoconductive surface is the same as the charge on the toner particles on the brush segment so that they are repelled therefrom to clean the toner particles from the brush.

United States Patent [191 Leenhouts Dec. 25, 1973 [75] Inventor: DonaldD. Leenhouts, Rochester,

[73] Assignee: Eastman Kodak Company,

Rochester, N.Y.

[22] Filed: June 9, 1972 [21] App]. No.: 261,478

Related US. Application Data [63] Continuation of Ser. No. 88,628, Nov.12, 1970,

2,741,959 4/1956 Rheinfrank et al 15/l.5 X

2,752,271 6/1956 Walkup et al. 15/1.5 X 3,313,623 4/1967 Bixby l5/1.5 X

Primary ExaminerLeon G. Machlin Attorney-Robert W. Hampton et al.

[57] ABSTRACT A residual toner image remaining after transfer of adeveloped image from a photoconductive surface is cleaned therefrom inone embodiment by a conductive cleaning brush mounted in a vacuumchamber and having a flicker bar which is used to apply a potential tothe brush opposite that of the residual toner particles to be removedfrom the photoconductive surface. In another embodiment, the brush isdivided into a number of electrically insulated segments so that thepolarity of the potential applied to a portion of the brush coming incontact with the photosensitive surface is opposite to the charge on theresidual toner particles and a potential applied to a segment spacedfrom the photoconductive surface is the same as the charge on the tonerparticles on the brush segment so that they are repelled therefrom toclean the toner particles from the brush.

9 Claims, 3 Drawing Figures PATENTEI] UEBZ 5 I973 INVENTOR.

DONALD 0. LEENHOUTS DEVELOPING STATION FIG. 2

BYD

ATTORNEYS APPARATUS FOR CLEANING A RESIDUAL IMAGE FROM A PHOTOSENSITIVEMEMBER This application is a continuation of application Ser. No.88,628, filed Nov. 12, 1970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to apparatus for removing electrostatically adhering particlesfrom a photoconductive member, and more particularly to improvedapparatus for cleaning residual toner particles from anelectrophotoconductive surface.

2. Description of the Prior Art In a conventional electrophotographicprocess, an electrostatic image is formed on a photoconductive surfaceas by placing a uniform electrostatic charge on the photoconductivesurface which surface is subsequently exposed to a radiation pattern todissipate the charge in the exposed areas. This image is then toned by asuitable developing material, such as dry toner powder. The developedimage is then transferred to a receiver. However, a small amount ofresidual toner usually remains on the photoconductive surface which mustbe removed therefrom prior to the forming and transfer of subsequentimages to prevent ghost images from being formed during subsequenttransfers.

Various attempts have been made to clean photoconductive surfaces. Onemethod of cleaning a photoconductive surface utilizes a rotating brush.One example of a rotating cleaning brush is disclosed in US. Pat. No.2,751,616 to Turner et al wherein the brush is treated with animpregnating material to control its conductivity. The brush is mountedwithin a dust hood and provided with a grounded flicker bar thatcontacts the brush fibers just before the brush contacts thephotoconductor. The electrical conductivity of the brush and flicker barassist in the neutralization of the residual charge on the tonerparticles. US. Pat. No. 2,752,271 to Walkup et al discloses the placingof a negative electrostatic charge on the photoconductive surfacecarrying the residual image and then rapidly brushing thephotoconductive surface in the presence of a vacuum. To counteract theelectrostatic attraction between the brush and particles to facilitatethe release of such particles to the vacuum, an electrostatic charge isapplied to the brush following brushing of the photoconductive surface.US. Pat. No. 3,313,623 to Bixby discloses a rotatable cleaning brush towhich a potential is applied to assist in removal of toner from aphotoconductive surface. In some environments, such cleaning deviceshave not been found entirely satisfactory. Residual toner particlesremaining on the photoconductive surface and/or cleaning element haveresulted in scumming and scratching of the photoconductive surface.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an improved apparatus for cleaning toner particles from aphotoconductive surface.

Another object of the invention is to provide an improved apparatus forcleaning residual toner particles remaining after transfer of adeveloped image from a photoconductive surface.

Yet another object of the invention is to provide improved apparatus forcontinuously removing toner particles from a cleaning brush.

Still another object of the invention is to remove residual tonerparticles from a photoconductive surface with reduced scumming andscratching of the surface.

These and other objects are accomplished in accordance with onedisclosed embodiment of the invention, by providing an electricallyconductive cleaning brush mounted in an air flow or vacuum chamber, towhich brush an electrical potential is applied by means of a flicker barthat contacts the fibrous brush material as the brush rotates.Maintaining the brush at a potential relative to ground attracts theresidual toner particles to the brush by overcoming the electrostaticforces which hold the particles to the photoconductive surface. Theflicker bar loosens the toner particles from the brush so that they arecarried away from the brush by the air flow. In some cases, some of theresidual toner particles will have a potential of positive polarity andothers a potential of negative polarity. In these cases the speed andefficiency of the cleaning operation can be improved by applying to theresidual toned image a charge of a polarity opposite to that applied tothe cleaning brush before contacting the brush with the photoconductivesurface. A flooding light is then used to reduce any potential remainingon the untoned areas of the photoconductive surfaces.

In another disclosed embodiment of the invention a cleaning brush isprovided with a number of segments each electrically insulated from eachother. A first flicker bar is utilized to apply a potential to a segmentof the brush to attract the toner particles to this segment as thissegment wipes or rubs against the photoconductive surface and a secondflicker bar is utilized to apply an opposite potential to a brushsegment when the segment is no longer in contact with thephotoconductive surface to repel the toner particles from that segmentof the brush for removal by the air flow.

Other objects and advantages of the invention will become apparent fromthe detailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description of thepreferred embodiments of the invention presented below, reference ismade to the accompanying drawings wherein corresponding parts areidentified by like numerals and in which:

FIG. 1 is a diagrammatic side elevation, partly in section, showing oneembodiment of the present invention for cleaning a photoconductive beltof a conventional electrophotographic mechanism.

FIG. 2 is a fragmentary side elevation, partly in section, similar toFIG. 1, showing additional apparatus for charging and illuminating thephotoconductive belt.

FIG. 3 is a fragmentary side elevation, partly in section, similar toFIG. 2, but showing another embodiment of the invention utilizing asegmented brush.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsand in particular to FIG. 1, there is shown an electrophotographicmechanism M, which includes an endless photoconductive belt 2 extendingaround spaced rollers 4 and 6 and is illustrated as being driven bymotor 8 through a drive belt 10. The belt 2 is driven past a chargingstation 12 which places a uniform electrical charge (either positive ornegative) over its photoconductive surface; an

exposure station 14 whereat the belt is exposed to a radiation pattern,such as a light image from an original, to discharge the photoconductivesurface in accordance with the radiation pattern to form anelectrostatic latent image; a developing station 16 whereat the latentimage is developed by depositing toner thereon; a transfer station 18whereat the developed image is transferred to a receiver; and finally anovel cleaning apparatus C whereat the photoconductive surface of thebelt 2 is cleaned of residual toner particles, The charging, exposure,developing and transfer stations can be of any form known in the priorart, and may be selected as required by one skilled in the art.

Cleaning apparatus C includes a rotatable brush 22 which may be made ofa soft fibrous material such as natural or artificial fur or flannelthat has been rendered electrically conductive, as for example, byimpregnating the brush fibers with nickel. The brush 22 is rotatablymounted as shown so that a portion of the brush fibers contacts the areaof the photoconductive belt 2 to be cleaned. A platen 24 on the side ofthe photoconductive belt 2 opposite that of the brush 22 is provided tosupport the belt in frictional contact with the brush. Alternatively,platen 24 can be replaced by a roller. Advantageously, the brush 22 isrotated by means (not shown) so that it moves in a direction opposite tothe movement of the photoconductive belt 2 at the point of contacttherewith. An electrical potential opposite in polarity to the charge onthe residual toner particles is applied to the brush 22, which iselectrically isolated from its mountings, from a source 28 by means of ametal contactor 26 which touches the brush fibers as the brush rotates.Conveniently, the contactor 26 is also used as a flicker bar to loosenthe toner particles attracted to the brush 22.

A shroud or housing 30 extends around a substantial portion of the brush22 as shown, and is illustrated as being provided with an air inlet 32and an air outlet 34 to which a vacuum can be applied to provide airmoving means to withdraw the toner particles removed from the belt 2from the vicinity of the brush. The toner particles are carried by theair flow to a disposable filter bag (not shown) or other equivalentdevice which can be easily replaced when the electrophotographicmechanism is normally shut down.

It has been found that in certain instances that some of the residualtoner'particles have a potential of positive polarity while otherparticles have a potential of negative polarity. In such instances, theconductive brush 22 with fibers charged to one polarity are not aseffective in removing toner particles of the same polarity as thefibers. In such cases the speed and efficiency of the cleaning apparatusC can be improved as shown in FIG. 2 by providing means, such as acorona discharge device 36 upstream of brush 22. The corona 36 applies auniform charge to the photoconductive surface of the belt 2 and theresidual toner image of a polarity opposite to the potential applied tothe brush 22 by the source 28. The charging by the corona 36 increasesthe charge on the residual image and increases the attraction betweenthe image and the brush fibers. To reduce the charge in the untonedareas of the photoconductive belt 2 and thereby decrease the attractionbetween the photoconductive belt and the residual toner image, thecorona charging is either accompanied by or followed by a flooding light38 which is directed onto the photoconductive surface of the belt.

Flooding light 38 also prevents charge buildup on the photoconductivesurface as a result of charging with corona 36.

In the embodiment of the invention shown in FIG. 3, electrophotographicmechanism M includes cleaning apparatus C having a conductive cleaningbrush 39, which is illustrated as having an insulative core 40 withspaced radial fins 41 to divide the brush into a plurality of segments,such as segments 42, 44, 46 and 48 respectively, each electricallyinsulated from the others. The brush segments are made of fur or othersoft fibrous material that have been treated with an electricallyconductive impregnating material. An electrical potential which willattract the residual toner particles during the wiping of thephotoconductive surface of the belt 2 is applied to the brush fibers ofeach brush segment from a source 50 through a metal contactor 52 as thebrush segments 42, 44, 46 and 48 pass the contactor 52. In FIG. 3,contactor 52 is shown applying an electrical potential to the brushfibers of brush segment 48. After the brush fibers have wiped thephotoconductive surface of the belt 2 and are no longer in engagementtherewith, an opposite potential which will repel the toner particlesfrom the brush fibers is applied to each brush segment from a source 54through a metal contactor 56 as the brush segments pass the contactor56. In FIG. 3, contactor 56 is shown applying such potential to thebrush fibers of brush segment 44. The metal contactors 52 and 56, insimilarity to contactor 26, also function as flicker bars. Contactor 52compresses the brush fibers of the brush 39 as they pass thereby. Afterbeing compressed by the contactor 52, the brush fibers spring outwardassisted by centrifugal force and contact the photoconductive surface ofthe belt 2 with more than normal wiping force. Contactor 56 functions toassist in loosening the toner particles from the brush fibers so thatthey may be removed by vacuum means which includes shroud 58.

Optionally, the corona discharge device 36 and source of illumination 38may be included, as previously described with respect to FIG. 2, toassist in removing bi-polar toner particles. Removal of bi-polar tonerparticles from the brush may be further assisted by utilizingalternating current for the source of potential 54 so that toner of bothpolarities will be repelled from the brush.

From the foregoing, the advantages of the present invention are readilyapparent. Novel cleaning apparatus and methodshave been disclosed whichcontinuously remove toner particles from the brush. This is accomplishedby use of a conductive member which serves the dual function of aflicker bar and a device for applying a potential to a cleaning brush.Accumulation of toner particles on the brush is, therefore, held tominimum levels to reduce scumming and the possibility of damage to thephotoconductive surface.

The invention has been described in detail with reference to preferredembodiments thereof, but it will be understood that variations andmodifications can be effected within the spirit and scope of theinvention.

I claim:

1. A cleaning device for cleaning residual toner particles, at leastsome of said residual toner particles having a charge of a firstpolarity thereon, from a photoconductive surface, said cleaning devicecomprising:

a. an electrically conductive, movable, fibrous cleaning element, saidelement being divided into at least first and second electricallyinsulated segments;

b. means for mounting said element so that a portion of the elementfibers contacts said photoconductive surface;

c. means for moving said element relative to said photoconductivesurface along an endless path;

d. first flicking means mounted in interference relation to the fibersof said element, said first flicking means being positioned to contactsaid segments of said element before said segments contact saidphotoconductive surface;

e. second flicking means mounted in interference re lation to the fibersof said element, said second flicking means being positioned to contactsaid segments of said element after said segments contact saidphotoconductive surface to dislodge toner particles from saidsegments;and

potential applying means for applying an electrical potential to saidfirst flicking means of a second and opposite polarity of that of theresidual toner particles so that said toner particles are attracted tosaid segments of said element.

2. Apparatus for removing residual toner particles from aphotoconductive surface, said apparatus comprising:

a. a movable element, said element including at least first and secondelectrically conductive segments, said segments being electricallyinsulated from each other;

b. means for mounting said element so that said segments aresequentially movable between a charging position whereat said segmentsare charged to a first potential, a contacting position whereat at leastone of said segments contacts the photoconductive surface, and aremoving position whereat said segments are charged to a secondpotential;

c. means for sequentially moving said segments between said charging,contacting and removing positions;

d. first potential applying means cooperatively associated with saidsegments at said charging position for applying a first potential tosaid segments prior to said segments contacting the photoconductivesurface, said first potential being of a polarity and magnitudesufficient to attract the residual toner particles from thephotoconductive surface to said segments charged to said firstpotential; and

e. second potential applying means cooperatively associated with saidsegments at said removing position for applying a second potential tosaid segments after completion of said segments contact with thephotoconductive surface, said second potential being of a polarity andmagnitude sufficient to repel the residual toner particles from saidsegments.

3. A cleaning device as claimed in claim 1, further including:

means for moving air relative to said element to with draw from thevicinity of said element toner particles dislodged from said segments.

4. A cleaning device as claimed in claim 1 wherein some of said residualtoner particles are charged to said first polarity and other of saidresidual particles are charged to said second opposite polarity, saidcleaning device further comprising:

potential applying means for applying an alternating potential to saidsecond flicking means to repel toner particles from said segments ofsaid element.

5. A cleaning device for cleaning electrically charged residual tonerparticles from a photoconductive surface, said device comprising:

a. an electrically conductive, rotatable cleaning brush mounted within ashroud, said brush being divided into at least first and secondelectrically insulated segments;

b. means for mounting said brush so that a portion of the brush fiberscontacts the photoconductive surface;

c. means for rotating said brush;

d. means to cause relative motion between the axis of said brush and thephotoconductive surface;

e. charging means for applying a uniform electrical charge of a firstpolarity to the photoconductive surface and the residual toner particlesprior to the surfaces contacting said brush;

f. a first electrically conductive contactor mounted in interferencerelation to the brush fibers, said first contactor being positioned sothat it contacts said brush segment before said brush segments contactthe photoconductive surface;

g. potential applying means connected to said first contactor forapplying to the brush fibers an electrical potential of a secondpolarity opposite said first polarity to attract the residual tonerparticles from the photoconductive surface to said brush segments;

h. a second electrically conductive contactor mounted in intereferencerelation to the brush fibers, said second contactor being positioned sothat it contacts said brush segments after said brush segments contactthe photoconductive surface to dislodge toner particles from said brushsegments; and

i. vacuum means connected to said shroud for withdrawing from thevicinity of said brush an airstream containing therein suspended tonerparticles dislodged from said brush.

6. A cleaning device as claimed in claim 5 further in cluding:

second potential applying means for applying to said second contactor anelectrical potential of said first polarity to repel toner particlesfrom said brush segments.

7. A cleaning device as claimed in claim 5, further including:

means for illuminating said photoconductive surface to actinic radiationprior to said surface s contacting said brush.

8. A cleaning device as claimed in claim 7 wherein said illuminatingmeans is activated subsequently to said charging means.

9. A cleaning device for cleaning residual toner particles from aphotoconductive surface, some of the residual toner particles beingcharged to a first polarity and other of said residual toner particlesbeing charged to a second polarity, said cleaning device comprising:

a. an electrically conductive, rotatable cleaning brush mounted within ashroud, said brush being divided into at least first and secondelectrically insulated segments;

b. means for mounting said brush so that a portion of the brush fiberscontact said photoconductive surface; c. means for rapidly rotating saidbrush; d. means to cause relative motion between the axis of said brushand said photoconductive surface;

,e. a first electrically conductive contactor mounted in interferencerelation to the brush fibers, said first contactor being positioned tocontact said segments of said brush before said segments contact saidphotoconductive surface;

f. a second electrically conductive contactor mounted in interferencerelation to the brush fibers, said second contactor being positioned tocontact said segments of said brush after said segments contact saidphotoconductive surface to dislodge toner particles from said brush;

g. a corona discharge electrode positioned and disposed to apply auniform electrostatic charge of said first polarity to saidphotoconductive surface ahead of said brush in the direction of movementof said photoconductive surface;

h. a source of illumination positioned and disposed to illuminate saidphotoconductive surface to actinic radiation downstream of said coronadischarge electrode and ahead of said brush in the direction of movementof said photoconductive surface;

. a source of direct current potential connected to said first contactorfor applying to said brush segments an electrical potential of saidsecond polarity so that said residual toner particles are attracted tosaid brush segments;

j. a source of alternating current potential connected to said secondcontactor for applying to said brush segments electrical potentials ofsaid first and second polarities to repel said toner particles from saidbrush segments; and

k. vacuum means connected to said shroud for withdrawing from thevicinity of said brush an airstream containing therein suspended tonerparticles dislodged from said segments of said brush.

1. A cleaning device for cleaning residual toner particles, at leastsome of said residual toner particles having a charge of a firstpolarity thereon, from a photoconductive surface, said cleaning devicecomprising: a. an electrically conductive, movable, fibrous cleaningelement, said element being divided into at least first and secondelectrically insulated segments; b. means for mounting said element sothat a portion of the element fibers contacts said photoconductivesurface; c. means for moving said element relative to saidphotoconductive surface along an endless path; d. first flicking meansmounted in interference relation to the fibers of said element, saidfirst flicking means being positioned to contact said segments of saidelement before said segments contact said photoconductive surface; e.second flicking means mounted in interference relation to the fibers ofsaid element, said second flicking means being positioned to contactsaid segments of said element after said segments contact saidphotoconductive surface to dislodge toner particles from said Segments;and f. potential applying means for applying an electrical potential tosaid first flicking means of a second and opposite polarity of that ofthe residual toner particles so that said toner particles are attractedto said segments of said element.
 2. Apparatus for removing residualtoner particles from a photoconductive surface, said apparatuscomprising: a. a movable element, said element including at least firstand second electrically conductive segments, said segments beingelectrically insulated from each other; b. means for mounting saidelement so that said segments are sequentially movable between acharging position whereat said segments are charged to a firstpotential, a contacting position whereat at least one of said segmentscontacts the photoconductive surface, and a removing position whereatsaid segments are charged to a second potential; c. means forsequentially moving said segments between said charging, contacting andremoving positions; d. first potential applying means cooperativelyassociated with said segments at said charging position for applying afirst potential to said segments prior to said segments contacting thephotoconductive surface, said first potential being of a polarity andmagnitude sufficient to attract the residual toner particles from thephotoconductive surface to said segments charged to said firstpotential; and e. second potential applying means cooperativelyassociated with said segments at said removing position for applying asecond potential to said segments after completion of said segmentscontact with the photoconductive surface, said second potential being ofa polarity and magnitude sufficient to repel the residual tonerparticles from said segments.
 3. A cleaning device as claimed in claim1, further including: means for moving air relative to said element towithdraw from the vicinity of said element toner particles dislodgedfrom said segments.
 4. A cleaning device as claimed in claim 1 whereinsome of said residual toner particles are charged to said first polarityand other of said residual particles are charged to said second oppositepolarity, said cleaning device further comprising: potential applyingmeans for applying an alternating potential to said second flickingmeans to repel toner particles from said segments of said element.
 5. Acleaning device for cleaning electrically charged residual tonerparticles from a photoconductive surface, said device comprising: a. anelectrically conductive, rotatable cleaning brush mounted within ashroud, said brush being divided into at least first and secondelectrically insulated segments; b. means for mounting said brush sothat a portion of the brush fibers contacts the photoconductive surface;c. means for rotating said brush; d. means to cause relative motionbetween the axis of said brush and the photoconductive surface; e.charging means for applying a uniform electrical charge of a firstpolarity to the photoconductive surface and the residual toner particlesprior to the surface''s contacting said brush; f. a first electricallyconductive contactor mounted in interference relation to the brushfibers, said first contactor being positioned so that it contacts saidbrush segment before said brush segments contact the photoconductivesurface; g. potential applying means connected to said first contactorfor applying to the brush fibers an electrical potential of a secondpolarity opposite said first polarity to attract the residual tonerparticles from the photoconductive surface to said brush segments; h. asecond electrically conductive contactor mounted in intereferencerelation to the brush fibers, said second contactor being positioned sothat it contacts said brush segments after said brush segments contactthe photoconductive surface to dislodge toner particles from said brushsegments; and i. vacuum means connected to said shroud for withdrawingfRom the vicinity of said brush an airstream containing thereinsuspended toner particles dislodged from said brush.
 6. A cleaningdevice as claimed in claim 5 further including: second potentialapplying means for applying to said second contactor an electricalpotential of said first polarity to repel toner particles from saidbrush segments.
 7. A cleaning device as claimed in claim 5, furtherincluding: means for illuminating said photoconductive surface toactinic radiation prior to said surface''s contacting said brush.
 8. Acleaning device as claimed in claim 7 wherein said illuminating means isactivated subsequently to said charging means.
 9. A cleaning device forcleaning residual toner particles from a photoconductive surface, someof the residual toner particles being charged to a first polarity andother of said residual toner particles being charged to a secondpolarity, said cleaning device comprising: a. an electricallyconductive, rotatable cleaning brush mounted within a shroud, said brushbeing divided into at least first and second electrically insulatedsegments; b. means for mounting said brush so that a portion of thebrush fibers contact said photoconductive surface; c. means for rapidlyrotating said brush; d. means to cause relative motion between the axisof said brush and said photoconductive surface; e. a first electricallyconductive contactor mounted in interference relation to the brushfibers, said first contactor being positioned to contact said segmentsof said brush before said segments contact said photoconductive surface;f. a second electrically conductive contactor mounted in interferencerelation to the brush fibers, said second contactor being positioned tocontact said segments of said brush after said segments contact saidphotoconductive surface to dislodge toner particles from said brush; g.a corona discharge electrode positioned and disposed to apply a uniformelectrostatic charge of said first polarity to said photoconductivesurface ahead of said brush in the direction of movement of saidphotoconductive surface; h. a source of illumination positioned anddisposed to illuminate said photoconductive surface to actinic radiationdownstream of said corona discharge electrode and ahead of said brush inthe direction of movement of said photoconductive surface; i. a sourceof direct current potential connected to said first contactor forapplying to said brush segments an electrical potential of said secondpolarity so that said residual toner particles are attracted to saidbrush segments; j. a source of alternating current potential connectedto said second contactor for applying to said brush segments electricalpotentials of said first and second polarities to repel said tonerparticles from said brush segments; and k. vacuum means connected tosaid shroud for withdrawing from the vicinity of said brush an airstreamcontaining therein suspended toner particles dislodged from saidsegments of said brush.